Assay Method Information

Assay Name:  Coupled Nucleotide Exchange Assay
Description:  Purified GDP-bound KRAS protein (aa 1-169), containing both G12C and C118A amino acid substitutions and an N-terminal His-tag, was pre-incubated in assay buffer (25 mM HEPES pH 7.4, 10 mM MgCl2, and 0.01% Triton X-100) with serially diluted compound for either 2 h or 20 h. For all subsequent steps, DTT was added to the reaction buffer at a final concentration of 1 mM. Following compound pre-incubation, purified SOS protein (aa 564-1049) and GTP (Roche 10106399001) were added to the assay wells and incubated for an additional 30 min. To determine the extent of inhibition of SOS-mediated nucleotide exchange, purified GST-tagged cRAF (aa 1-149), nickel chelate AlphaLISA acceptor beads (PerkinElmer AL108R), and AlphaScreen glutathione donor beads (PerkinElmer 6765302) were added to the assay wells and incubated for 5 min. The assay plates were then read on a plate reader measuring luminescence signal. Signal intensity of compound-containing wells were normalized to DMSO control, and data were analyzed using a 4-parameter logistic model to calculate IC50 values.
Affinity data for this assay
 

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